Describe the issue

Signmessage doesn't work on "segwit addresses" (what BIP141/BIP49 calls "P2WPKH-nested-in-P2SH").

Steps to reproduce

On testnet (or on litecoin :)):

1. NEW_ADDRESS=$(bitcoin-cli getnewaddress)
2. SEGWIT_ADDRESS=$(bitcoin-cli addwitnessaddress $NEW_ADDRESS)
3. bitcoin-cli signmessage $SEGWIT_ADDRESS "shiny"

Expected behaviour

Signature is printed

Actual behaviour

error code: -3
error message:
Address does not refer to key

What version of bitcoin-core are you using?

v0.14.1

self-compiled from github repo

Machine specs:

• OS: Linux
• CPU: can reproduce on x86 and x64 CPUs